Many people ask why Easter under the Orthodox Church is often celebrated on a different date to that of the Western Churches, Catholic and Protestant. The question is justified, for we live in a situation in which the majority of Christendom celebrates Easter under the Western tradition.

The precise determination of the date of Easter has preoccupied Christians throughout the history of the Church and has been a divisive factor which continues to the present day to be a source of controversy between the Eastern and Western Churches.

Those Christians who originally converted from Judaism celebrated Easter in accordance with the Jewish calendar, on the same day that the feast of the Passover, 'Pascha', was celebrated, that day being the 14th of the lunar month of Nisan, regardless of the day of the week upon which it fell. The Churches of Asia Minor followed this practice whilst the other Churches both in the East and in the West, always celebrated Easter on the Sunday following this date.

The Christians of Asia Minor held that this date was that of the crucifixion of Christ, whilst the Christians of the other Eastern and Western Churches believed it to be the date of the Last Supper, held on the day preceding the crucifixion and being a Passover meal. The Gospel, of Saint John asserts the former and the Synoptic Gospels assert the latter, a discrepancy for which an explanation has been attempted by pointing out that the Synoptic Gospels followed Jewish practice in considering the 14th of Nisan to have begun on the previous evening and hence, from a calendar point of view, on the evening of 13th of Nisan.

By the third century AD, all the Churches had agreed upon celebrating Easter on the Sunday following 14th of Nisan. This date was determined in accordance with the Jewish calculation of Passover, on the first full moon following the vernal equinox. Following the destruction of Jerusalem in AD 70, however, the Jews of the Diaspora depended upon local pagan calendars for their calculations. The feast of Passover consequently sometimes preceded the vernal equinox and most Christians abandoned the practice of regulating the date of Easter through the date of Passover in order to avoid the inaccuracy occasioned by the dependence on these calendars.

The alternative to depending upon Passover for the determination of a date for Easter was the system of 'paschal cycles', each paschal cycle having a duration of several years, throughout which the full moon occurs on the same day of the year, with only some exceptions. Once again differences in the employment of these cycles arose between the Eastern and Western Churches; the Eastern Church adopted a 19-year cycle whereas the Western Church employed a less accurate 84-year cycle, which resulted in more differences. In the West the vernal equinox was observed on 18th March, while in the East it was observed on 21st March.

The issue was finally brought before the First Ecumenical Synod at Nicaea in AD 325, which decreed that Easter must not be calculated according to Passover, but that it must be celebrated after the vernal equinox, specifically, on the Sunday following the first full moon occurring after the date of the vernal equinox. Subsequently, the regulation concerning Passover was interpreted as requiring that Easter be celebrated after Passover. The Eastern Church then reverted to the original method for the determination of the date of Passover and consequently of Easter.

Since AD 325 the “loss of time” has resulted in a “forwarding” of calendar dates and hence 21st March at the time of the Synod at Nicaea now corresponds with 3rd April. Therefore Easter may not be celebrated before this date or after 8th May by the Orthodox Church.

Although the Eastern Church has neglected consideration for the progressive loss of time since AD 325, the Western Church has also neglected this, in addition to not having taken into account either the original method for the determination of the Passover date or the accurate determination of the vernal equinox, without which an accurate determination of the date of Easter is impossible. The present discrepancy is consequently a result of all the above-mentioned factors and will not be resolved unless new standards of accuracy are sought and effected.